#65 unbiased_random

src/solutions/chapter5/section1/exercise3.py

@@ -0,0 +1,16 @@
+from random import uniform
+
+p = uniform(0, 1)
+
+
+def unbiased_random():
+    while True:
+        x = __biased_random()
+        y = __biased_random()
+        if x != y:
+            break
+    return x
+
+
+def __biased_random():
+    return 1 if uniform(0, 1) <= p else 0

test/test_solutions/test_chapter5.py

@@ -3,6 +3,7 @@
 from hypothesis import strategies as st
 
 from solutions.chapter5.section1.exercise2 import random
+from solutions.chapter5.section1.exercise3 import unbiased_random
 from test_case import ClrsTestCase
 from util import range_of
 
@@ -18,3 +19,15 @@ def test_random(self, data):
         x = random(a, b)
 
         self.assertIn(x, range_of(a, to=b))
+
+    def test_unbiased_random(self):
+        samples = 1000
+        count0 = 0
+        for _ in range_of(1, to=samples):
+
+            x = unbiased_random()
+
+            self.assertIn(x, range_of(0, to=1))
+            if x == 0:
+                count0 += 1
+        self.assertAlmostEqual(count0 / samples, 0.5, delta=0.1)